Watts to Kilowatt-Hours (kWh) Conversion Calculator

Convert watts to kilowatt-hours by entering power in watts and time in hours.

Energy in Kilowatt-Hours:

Learn how we calculated this below

scroll down

On this page:

How to Convert Watts to Kilowatt-Hours

A kilowatt-hour, expressed as kWh or kW·h, is a measure of energy that is equivalent to 1,000 watts of power for a 1-hour time period. Thus, to convert watts to kilowatt-hours, multiply the power in watts by the number of hours, then divide by 1,000.

Watts to kWh Formula

Use the following formula to calculate energy in kilowatt-hours:

E(kWh) = P(W) × T(hrs) / 1,000

The energy E in kilowatt-hours is equal to the power P consumed in watts times the time T in hours, divided by 1,000.

For example: let’s find the kWh of 1,500 watts for 2.5 hours.

E(kWh) = 1,500 × 2.5 / 1,000
E(kWh) = 3,750 Wh / 1,000
E(kWh) = 3.75 kWh

Thus, the energy in kilowatt hours for a 1,500 power consumption over 2.5 hours is equal to 3.75 kilowatt-hours.

You can also use this formula to convert kilowatts to kilowatt-hours by not dividing by 1,000.

watts to kWh formula showing that the energy in kilowatt-hours is equal to the power in watts times the time in hours, divided by 1,000

Electricity usage is often measured in watt-hours or kilowatt-hours, so if you can convert watts to kWh, then you can predict how much an electric appliance might cost, or how much energy is required to power it.

For example: let’s predict how much it costs to power a light bulb every hour. A 100-watt light bulb uses 100 watts of power. To convert the power in watts to kilowatt-hours, multiply 100 watts by 1 hour, then divide by 1,000 to find the energy usage in kWh.

E(kWh) = 100 W × 1 hour / 1,000
E(kWh) = 100 Wh / 1,000
E(kWh) = 0.1 kWh

If electricity costs $0.12 per kWh, then a 100-watt light bulb will cost 1.2 cents per hour that it’s on.

Try our electricity cost calculator to estimate the cost of power usage on your monthly bill.

Common Watts to Kilowatt-Hour Conversions

Common watts to kilowatt-hour conversions for a 1-hour time period, along with the estimated cost of electricity, assuming a price of $0.12 per kWh.
Power in Watts Energy in Kilowatt-hours Electricity Cost (at $0.12/kWh)
100 W 0.1 kWh $0.012 per hr
200 W 0.2 kWh $0.024 per hr
300 W 0.3 kWh $0.036 per hr
400 W 0.4 kWh $0.048 per hr
500 W 0.5 kWh $0.060 per hr
600 W 0.6 kWh $0.072 per hr
700 W 0.7 kWh $0.084 per hr
800 W 0.8 kWh $0.096 per hr
900 W 0.9 kWh $0.108 per hr
1000 W 1 kWh $0.112 per hr

To convert energy to watts, use our kWh to watts conversion calculator.